GM-CSF was detected by Singulex bead-based immunoassay in 3/18 HCs, 2/18 RA patients, 4/20 AS patients naïve for biologic treatment, 5/18 AS patients on biologic treatment, and 5/8 AS patients studied both pre- and on TNFi treatment, totalling 14/46 (30%) AS patients compared to 3/18 (17%) HC (Supplementary Table 5). Here, CSF2 is linked to rheumatoid arthritis.